The monitoring group, which relies on a network of activists in Syria, said the hospital is no longer operational. Save the Children said the maternity hospital is the only such facility in the area, with the next unit 40 miles away.

The hospital opened in 2014 and has an on-call paediatrician and six incubators for premature babies.

Meanwhile, Syrian activists said a US-led coalition air strike targeting a village in northern Syria held by the Islamic State group had killed 28 civilians including seven children.

Syrian Observatory for Human Rights chief Rami Adurrahman said another 13 people were killed in the strikes on Al-Ghandour, near the Turkish border, but he could not say if they were IS fighters or civilians.

Al-Ghandour is 15 miles north west of the town of Manbij, a key hub in the extremist group's Syria network and a supply route to IS's de facto capital of Raqqa.

The bombings came a week after air strikes, also blamed by Syrian activists on US aircraft, killed at least 56 civilians in IS-held territory in northern Syria.

The Manbij area has seen extensive battles between IS extremists and US-backed Kurdish-led fighters, who have been advancing under the cover of air strikes by the US-led coalition. The town is encircled by the Kurdish-led Syrian Democratic Forces.

The SDF extricated another 1,000 civilians from Manbij on Thursday, according to Mustafa Bali, a local media activist living in the town of Kobani.

Elsewhere, the Observatory said IS militants had recaptured the nearby village of al-Bouweir and killed 24 civilians.

Hamoud Almousa, a founding member of Raqqa is Being Slaughtered Silently, an activist group, said IS sought retribution from the village for "not defending Islam" when the SDF drove out IS earlier this summer.

Mr Almousa said most of the villagers fled before the extremists retook al-Bouweir but the men who remained were killed.

In Geneva, the UN special envoy for Syria urged Russia to leave the creation of any humanitarian corridors around the embattled northern city of Aleppo to the United Nations and its partners.

"That's our job," said Staffan de Mistura as he explained his "suggestion" to Moscow at a press conference, a day after Russia said its forces and those of the Syrian government would open humanitarian corridors around Aleppo and offer a way out for civilians and surrendering fighters.

He expressed support "in principle" for humanitarian corridors "under the right circumstances", but he is awaiting clarification from Russian authorities about the plan, noting the urgent situation in the northern city, and adding: "The clock is ticking for the Aleppo population."

"How do you expect people to walk through a corridor - thousands of them - while there is shelling, bombing, fighting?" Mr de Mistura said.

He added that no-one should be forced to leave Aleppo, but "indeed, some civilians may want to avail themselves of the possibility afforded by the corridor and by the Russian initiative. When they do, it is crucial that they be given the option of leaving to areas of their own choice".

Mr de Mistura also praised a statement from the International Committee of the Red Cross about the Russian proposal, which said any such corridors should have the "consent of all parties on all sides". ICRC regional director for the Middle East, Robert Mardini, said he had no indication all sides were on board with the plan.